In general, the lithographic offset printing method and the letterpress printing method are well-known in the art as printing methods or processes for performing multicolor printing operations upon a container fabricated from various materials, such as, for example, metal, glass, plastic, paper, or the like. In accordance with the techniques characteristic of the lithographic offset printing method, ink adheres to a picture-line portion of a lithograph as a result of the picture-line portion of the lithograph being provided with a lipophilic property, while the non-picture-line portion of the lithograph exhibits or is provided with a hydrophilic property. The ink upon the lithograph is then transferred to a rubber blanket, and in turn, the ink disposed upon the rubber blanket is finally transferred to a material or object to be printed.
Similarly, in accordance with the techniques characteristic of the letterpress printing method, ink is applied to the picture-line portion which is provided upon a press in the form of a relief, and subsequently, the ink is transferred onto a material or object to be printed.
The aforenoted conventional printing methods, processes, and techniques are therefore appreciated as being superior in connection with the mass production of printed materials or objects, however, such methods or techniques do in fact require the pre-fabrication of the requisite printing plates or the like which of course entail considerable manufacturing costs, time, and labor, before the same are even used in connection with the actual printing operation to be performed upon the material or object to be printed. Accordingly, it can be further appreciated that such conventional multicolor printing processes or methods involve considerably or substantially more time and labor when it is in fact desired to print or register the respectively different colors of the multicolor printing operation upon the material or object to be printed.
Recently, electronic techniques have been developed within the printing technological field, such as, for example, the use of computerization, utilizing a layout scanner, in connection with an original manufacturing operation, and the development of a direct plate-making system for use within a plate-making process, however, techniques have nevertheless not as yet been developed for permitting elimination of the plate-making process per se for manufacturing the requisite printing plates, and consequently, the drawbacks and deficiencies of the prior art or conventional systems, processes, methods, and techniques still exist and remain.
Still further, in accordance with individual preferences, tastes, and pre-selected designs, there are increasing requirements for printing such various designs or indicia upon multiple kinds of materials and products, and consequently, it is becoming ever-increasingly more difficult to satisfy or achieve such requirements by means of such aforenoted conventional printing methods and techniques which are not particularly adaptable to readily alterable or adjustable printing functions or operations.
Considering then entirely different or alternate types printing techniques, such as, for example, those processes or techniques which do not require the use of printing plates, the electro-photographic printing method or the ink-jet printing method, also known as the non-impact printing technique, are in fact well-known. In accordance with these noted types of printing methods or techniques, a pictorial image can in fact be directly obtained by means of a pictorial image output from a computer without using a printing plate. In particular, the electrophotographic printing method has been widely utilized within photocopying machines, facsimile machines, and other types of printers whereby such method or technique has thus been employed in lieu of conventional printing methods or techniques.
More particularly, in accordance with a printing operation utilizing an electrophotographic printing method or technique, a surface of a photoconductive material is firstly uniformly charged, and subsequently, the surface is exposed from a position external to the photoconductive material so as to form an electrostatic latent image upon the surface of the photoconductive material. In order to then develop the electrostatic latent image and render the same visible, toner particles are deposited upon and adhere to the surface of the photoconductive material by means of a magnetic brushing method or technique, for example, whereupon, the toner particles are then transferred to a material or object to be printed and thermally fixed thereon, thereby completing the printing process.
When utilizing electrophotographic printing techniques in order to achieve multicolor printing processes, the multicolor printing process is performed and achieved by conducting an electrophotographic printing process utilizing a first color toner which, in accordance with the aforenoted techniques, is transferred to and fixed upon the material to be printed. Subsequently, the electrophotographic printing process is repeated so as to successively deposit, transfer, and fix other color toners upon the particular material being printed.
While the foregoing process or technique initially appears to be capable of being readily achieved or performed, the adaptation of such electrophotographic printing techniques in connection with multicolor printing processes does in fact involve substantial problems. For example, the process of transferring the toner image to the material or object being printed is very difficult to achieve, particularly in the case wherein the material or object to be printed is in fact a container. This is appreciated as being true because the transfer process is performed electrostatically wherein a gap exists or is defined between the toner image and the material or object being printed, in this case, the container. However, in view of the additional fact that the container may comprise one or more non-planar surfaces, it is very difficult to in fact achieve or define a constant gap space between the non-planar or curved surfaces of the container and the photoconductive drum upon which the toner image is formed.
Continuing further, in performance of a multicolor printing process, it is necessary, as has been noted hereinabove, to transfer toner images a multiplicity of times, that is, depending upon the number of color images or color components to be printed, and when the material or object to be printed is a container, it is quite difficult to properly register or align the container with the particular color image to be transferred thereto. In accordance with conventional techniques, a mark is usually applied to the material or object to be printed, and this mark is appropriately detected by suitable detection or sensing means, and accordingly, exposure for formation of the toner image is then conducted. However, in the instance that the material or object to be printed is a container, the mark detecting or sensing means, as well as the exposure means, is characterized by means of a relatively complex structure, and the registration or alignment process is quite difficult to achieve. Still further, in the instance wherein conventional electrophotographic printing techniques are utilized in conjunction with a metallic container, the photoconductive material may be damaged as a result of contact with the metallic container during the transfer process, and consequently, the photoconductive material may experience premature wear, and consequently, a substantially decreased service life.
Another conventional multicolor printing method, process, or technique utilized in conjunction with a material or object to be printed having a non-planar or curved surface is one in which a release agent is applied to a thin plastic film, called a base film, which is characterizied by means of a heat-resistant property; a color image picture is printed upon the base film by means of, for example, an offset printing method or process, or a gravure printing method or process; the base film, with the color image picture thereon, is then applied to the curved surface of the material or object to be printed; and a heated roll or roller is then pressed upon the rear surface of the base film so as to thereby transfer and fuse the thermoplastic resin forming the image picture from the base film onto the curved surface of the material or object being printed. This technique or thermo-transfer printing process is conventionally utilized as a printing method by means of which an image can be printed upon a surface having a complex curvature and upon which, or in connection with which, printing techniques utilizing a conventional press cannot be employed.
It is to be further realized or appreciated, however, that with the aforenoted thermo-transfer printing process or method, a plate is nevertheless utilized or still required in order to form the picture image upon the base film, and consequently, this method is characterized by means of the same problems or deficiencies noted hereinabove in connection with the plate-making procedures, as well as the registration of the respective colors forming the multi-color picture or image to be printed upon the material or object being printed. In addition, there is also a need or problem concerning disposal of an expensive base film.